I found a new version of you GUI some time ago and only now I've tested new function "embed previews to CR2" on group of files.
All works well, thanks a lot for your work. But there is one bug.
As I see, after converting via DPP all JPEGs have horizontal orientation, even if their actual orientation is vertical. It is not problem - your program checks orientation well.
The main problem is when we rotate image in DPP.
When in camera I set flag "rotate on PC screen" - all RAWs have in EXIF information about vertical orientation (camera writes it). In this case I can see RAW in all viewers correctly oriented. After DPP convertion to JPEG we have correctly oriented images too.
But, if I rotate image in DPP, orientation tag (which I can see in GUI) stays horisontal (or vertical). It does not change! We have to rotate images sometimes, especially if in camera we set "do not rotate".
After such rotation, I see image rotated in DPP, but it is not rotated in other viewers! I don't understand, where DPP writes information about rotation.
That's why we receive after DPP correctly oriented JPEG, but RAW is not rotated. We can not embed such JPEG in RAW, because in other viewers and cataloging programs we will see RAW incorrect.
May be it is bug of DPP? I use 3.5.1. version.
All the best!